08 - Strings

• Prefer string interpolation and string formatting instead of string concatenation:

  # bad
  email_with_name = user.name + ' <' + user.email + '>'
  
  # good
  email_with_name = "#{user.name} <#{user.email}>"
  
  # good
  email_with_name = format('%s <%s>', user.name, user.email)
  

• With interpolated expressions, there should be no padded-spacing inside the braces.

  # bad
  "From: #{ user.first_name }, #{ user.last_name }"
  
  # good
  "From: #{user.first_name}, #{user.last_name}"
  

• Adopt a consistent string literal quoting style. There are two popular styles in the Ruby community, both of which are considered good - single quotes by default (Option A) and double quotes by default (Option B).

  • (Option A) Prefer single-quoted strings when you don't need string interpolation or special symbols such as \t, \n, ', etc.

    # bad
    name = "Bozhidar"
    
    # good
    name = 'Bozhidar'
    

  • (Option B) Prefer double-quotes unless your string literal contains " or escape characters you want to suppress.

    # bad
    name = 'Bozhidar'
    
    # good
    name = "Bozhidar"
    

  The string literals in this guide are aligned with the first style.

• Don't use the character literal syntax ?x. Since Ruby 1.9 it's basically redundant - ?x would interpreted as 'x' (a string with a single character in it).

  # bad
  char = ?c
  
  # good
  char = 'c'
  

• Don't leave out {} around instance and global variables being interpolated into a string.

  class Person
    attr_reader :first_name, :last_name
  
    def initialize(first_name, last_name)
      @first_name = first_name
      @last_name = last_name
    end
  
    # bad - valid, but awkward
    def to_s
      "#@first_name #@last_name"
    end
  
    # good
    def to_s
      "#{@first_name} #{@last_name}"
    end
  end
  
  $global = 0
  # bad
  puts "$global = #$global"
  
  # good
  puts "$global = #{$global}"
  

• Don't use Object#to_s on interpolated objects. It's invoked on them automatically.

  # bad
  message = "This is the #{result.to_s}."
  
  # good
  message = "This is the #{result}."
  

• Avoid using String#+ when you need to construct large data chunks. Instead, use String#<<. Concatenation mutates the string instance in-place and is always faster than String#+, which creates a bunch of new string objects.

  # bad
  html = ''
  html += '<h1>Page title</h1>'
  
  paragraphs.each do |paragraph|
    html += "<p>#{paragraph}</p>"
  end
  
  # good and also fast
  html = ''
  html << '<h1>Page title</h1>'
  
  paragraphs.each do |paragraph|
    html << "<p>#{paragraph}</p>"
  end
  

• Don't use String#gsub in scenarios in which you can use a faster more specialized alternative.

    url = 'http://example.com'
    str = 'lisp-case-rules'
  
    # bad
    url.gsub('http://', 'https://')
    str.gsub('-', '_')
  
    # good
    url.sub('http://', 'https://')
    str.tr('-', '_')
  

• When using heredocs for multi-line strings keep in mind the fact that they preserve leading whitespace. It's a good practice to employ some margin based on which to trim the excessive whitespace.

  code = <<-END.gsub(/^\s+\|/, '')
    |def test
    |  some_method
    |  other_method
    |end
  END
  # => "def test\n  some_method\n  other_method\nend\n"
  

• Use Ruby 2.3's squiggly heredocs for nicely indented multiline strings.

  # bad - using Powerpack String#strip_margin
  code = <<-END.strip_margin('|')
    |def test
    |  some_method
    |  other_method
    |end
  END
  
  # also bad
  code = <<-END
  def test
    some_method
    other_method
  end
  END
  
  # good
  code = <<~END
    def test
      some_method
      other_method
    end
  END